Why does my Ads on my blog doesn't have any relevance with my Site?

Every time i visit to my blog it always show different ads not related to my topic or even the Blog itself. My site is about music and guitars but the ads are pointing to advertisements like computers, travel, cars, donations, etc. . Is it permanent or Google is fetching more related ads for my site?

It sometimes takes a while for Google to put the right ads on the site, especially if you have just placed the ads on your pages. Though computer and car ads are higher paying than music

However, if it's been a month since you've placed the ad and the ads are still showing PSAs (donations), then follow Google's tips on implementing SECTION TARGETING to improve ad targeting on your site

https://www.google.com/adsense/support/bin/answer.py?answer=23168&ctx=en:search&query=section+targeting&topic=&type=

What is section targeting and how do I implement it?

Section targeting allows you to suggest sections of your text and HTML content that you'd like us to emphasize or downplay when matching ads to your site's content. By providing us with your suggestions, you can assist us in improving your ad targeting. We recommend that only those familiar with HTML attempt to implement section targeting.

Optimize your blog for the search engines so that they pick up the relevant keywords :